1. Field of the Invention
The present invention relates to a technique for controlling enlargement of a dynamic range in an image capturing apparatus.
2. Description of the Related Art
In general, to obtain one image, there is known dynamic range enlargement control for composing a plurality of images into one image to generate an image having a wide dynamic range. This control aims at improving an image quality by generating a composite image using images shot under different exposure conditions. Since shooting is performed a plurality of times, the shooting timings of the respective images are different from each other. For example, when a moving object is shot, images may often be shot at different angles of view.
Japanese Patent Laid-Open No. 2008-109176 discloses a method of outputting a plurality of captured images by performing exposure a plurality of times and multiplying the output images by a gain calculated by a ratio of the average luminance value of reference image data and a reference luminance value, thereby equalizing the brightness of the reference image data and the brightness of non-reference image data to detect a position shift. Using the position shift detection result, the position shift of an image obtained before gain multiplication is corrected, and image composition is performed.
However, in Japanese Patent Laid-Open No. 2008-109176, for example, assume that an image is rotated for alignment. Since one image does not have peripheral pixels in image composition, as shown in FIG. 2, a desired image may not be obtained in the peripheral portion of the composite image.